Process for preparing alkyl aryl compounds



United States Patent 3,474,154 PROCESS FOR PREPARING ALKYL ARYLCOMPOUNDS Toshio Yamanaka, Shiro Yuki, and Haruo Shibatani,

Yokkaichi-shi, Japan, assignors to Mitsubishi Petrochemical Co., Ltd.

No Drawing. Filed Feb. 14, 1968, Ser. No. 705,304 Claims priority,application Japan, Feb. 17, 1967, 42/ 10,228; Apr. 28, 1967, 42/26,926Int. Cl. C07c 3/50 US. Cl. 260-671 6 Claims ABSTRACT OF THE DISCLOSUREIn a process for the production of an alkyl aryl compound by alkylatingaryl compounds with a mono-olefin having 8-18 carbon atoms in thepresence of hydrogen fluoride, the improvement which comprisesconducting said alkylation reaction at a temperature of from 0 to 35 C.to complete the reaction substantially, and then subjecting theresulting alkylation reaction product to a heat treatment at an elevatedtemperature of from 40 to 70 C. to give the desired alkyl aryl compound.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates to a process for alkylating aromatic hydrocarbons. Morespecifically, this invention relates to a process for producing alkylaryl compounds having excellent sulfonating characteristics byalkylation of aromatic hydrocarbons with a long chain monoolefin in thepresence of hydrogen fluoride as a reaction catalyst.

Description of the prior art Generally, alkyl aryl sulfonates used assynthetic detergents are produced by the steps of alkylating aromatichydrocarbons such as benzene, toluene and the like with long chainmono-olefin having about from 8 to 18 carbon atoms in the presence of aFriedel Crafts catalyst such as hydrogen fluoride and the like,fractionating the resulting alkylation product to separate desired alkylaryl compounds, i.e. detergent alkylate, sulfonating the alkyl arylcompound with a sulfonating agent such as sulfuric anhydride, fumingsulfuric acid, concentrated sulfuric acid and the like, and neutralizingthe resulting sulfonic acid with an alkaline material such as causticsoda and ammonia.

The alkyl aryl compound prepared by the processes known heretofore has atendency to produce colored sulfonate. That is, the sulfonate producedtherefrom has generally undesirable color, and is less valuable as acommercial product. In order to solve said coloring problem of thesulfonate, several processes including bleaching of the coloredsulfonate and refining of the starting alkyl aryl compound have beenproposed. For example, a process for treating alkyl aryl compounds withoxidizing agent in the presence of water and sulfuric acid, or treatingthe alkyl aryl compounds with benzene and hydrogen fluoride, in additionto the conventional decoloring process such as clay treatment andsulfuric acid treatment have been proposed.

However, these prior art processes known heretofore have disadvantagesin that there are required separation of alkylates and relativeexpensive reagents for purifying and that the purifying effect is notnecessarily remarkable, thus, they cannot be regarded as completelysatisfactory.

In the production of alkylate using a straight chain olefin as astarting material, alkyl benzene compounds "ice obtained therefrom aremixtures of various kinds of isomers having the structural formula:

wherein n is a number of carbon atoms in the starting olefin molecule,which is 8n18, and m is an integer of 0mn13. It is understood that thealkyl benzene compounds referred to above contain every and all isomershaving various values of m' satisfying the equation, 0mn3, regardless ofthe type of reactions by which these alkyl benzene compounds areproduced.

The isomer distribution in the alkyl benzene compounds depends upon thestarting materials and the type of reactions used. Possible differencein the isomer distribution may be shown by the difference in the contentof Z-phenyl alkane, which is an isomer having a value of m of zero.

The fact that the 2-pheny1 alkane content affects the properties of softdetergents obtained therefrom as described hereinafter is characteristicof the use of substantially straight chain alkylating agents since noimportant influence is caused by the difference in the position of aphenyl group upon using branched alkylating agents such as propylenetetramer, conventionally used heretofore.

Therefore, there is a certain problem to be solved in the production ofbiologically degradable soft detergents, which is not found in theproduction of hard type detergents.

Each soft alkyl benzene sulfonate obtained from alkyl benzene havinghigher Z-phenyl alkane content and from that having lower Z-phenylalkane content, may differ in its property as a detergent. For example,a sulfonate obtained from alkylate having a high 2-phenyl alkane contenthas excellent biodegradability, whereas a sulfonate obtained from thathaving a low Z-phenyl alkane content has a feature of excellent foamstability. Since both biodegradability and foam stability are desirableproperties as detergent, it is difiicult to determine which alkylate ispreferred to the other.

Therefore, choice of alkylate will depend on the desired property of thedetergent to be produced, or the manufacturers option.

There are many cases when alkylate having a lower 2-phenyl alkanecontent is required to prepare detergent having excellent foamstability.

When such alkylate is required, it is more preferable to employ thealkylation process using hydrogen fluoride catalyst than that usingaluminum chloride. But even in the process using hydrogen fluoridecatalyst, there is a case Where much lower 2-phenyl alkane content inalkylate is required, especially when using u-olefin as a startingmaterial, which gives higher 2-phenyl alkane content than internalolefin.

And on this occasion, it is necessary to employ special technique toreduce the content of 2-phenyl alkane.

SUMMARY OF THE INVENTION An object of this invention is to provide aprocess for obtaining alkyl aryl compounds having excellent sulfonatingcharacteristics, which may afford alkyl aryl sulfonate having noundesirable color.

Another object of this invention is to provide a process for producingan alkyl aryl compound, more specifically an alkyl benzene, of lower2-aryl alkane, more specifically 2-phenyl alkane content, which affordssulfonate free from undesirable coloration, from substantially straightchain mono-olefin and benzene using hydrogen fluoride catalyst.

As a result of our thorough study, we have found that an alkyl arylcompound capable of affording sutfonates having less undesirablecoloration may be obtained by conducting the alkylation reaction at40-70 C.

For example, when propylene tetramer or other branched olefin is reactedwith benzene at higher temperatures, decomposition of the olefin tendsto be increased, thus, the amount of lower molecular weight alkylate,i.e. light alkylate, in the alkylation product is increased, which, inturn, decreases the yield of the desired alkylate, though the colorationof sulfonates obtained therefrom may fairly be improved. Therefore, suchhigh-temperature reaction conditions may not be applicable directly tothe alkylation reaction using a branched olefin as alkylating agent.

We have found that if the alkylation reaction is substantially completedat lower temperatures and subsequently the reaction mixture is heated athigher temperature, there is observed practically no formation of shortchain alkyl aryl compound, affording the yield of alkylate as high asthat in the reaction employing lower temperatures throughout, and that,in addition, the resulting alkylate has a capability of improving thecolor of sulfonates derived therefrom.

Thus, in accordance with this invention, there is obtained alkylateshaving excellent sulfonating characteristics by conducting thealkylation reaction at a lower temperature and then subjecting theresulting alkylation product to a heating at a relatively highertemperature, without sacrificing the yield of the alkylate.

In the production of alkylate for detergent using straight chain olefinas a starting material and hydrogen fluoride as a catalyst, there is aclose relationship between the reaction temperature and 2-phenyl alkanecontent, i.e., 2-phenyl alkane content in the alkylate is decreased,when the reaction is carried out at low temperatures.

For example, when the alkylation is conducted at a temperature higherthan 35 C., 2-aryl alkane content in the alkylate would remarkably beincreased.

Thus, although there may be produced alkylate having lower 2-phenylalkane content by carrying out the alkylation at a temperature of fromto 35 C., there is a disadvantage in that the resulting alkylate tendsto give undesirably colored alkyl benzene sulfonates.

In accordance with this invention, an alkyl aryl compound havingexcellent sulfonating characteristics may be easily produced withoutaccompanying such disadvantage.

The process of this invention comprises the steps of (1) alkylating anaryl compound with a long chain monoolefin having 8-18 carbon atoms inthe presence of hydrogen fluoride catalyst at a temperature of from 0 to35 C., to complete the reaction substantially, and then (2) subjectingthe resultant alkylated reaction product to a heat treatment at anelevated temperature of from 40 to 70 C. to give alkyl aryl compoundshaving excellent sulfonating characteristics.

Although, in general, a satisfactory result may be obtained with regardto the yield of alkylate as well as to the 2-aryl alkane content atlower temperatures, considering the reaction velocity and the cost ofproduction of alkylate on a commercial scale, the above-mentioned firststep, i.e. the alkylation reaction according to the process of thisinvention is carried out at a temperature of from 0 to 35 C. Thereaction time employed in the first step may be from 5 to 50 minutes.

The alkylation reaction of the first step must be substantiallycompleted, e.g., more than 90% of theory, and the alkylation product isthen subjected to a heat treatment of the second step.

The second step of this process may be conducted without separating thealkylate from the reaction mixture.

As described above, the temperature and the time conditions of thesecond step of this process are limited to a specific range as mentionedabove. But, the temperature and time conditions employed in the secondstep are preferably determined by the alkylation temperature employed inthe first step.

The heat treatment of the second step is advantageously carried out at atemperature above 40 C., and the higher the temperature employed, thebetter result may be obtained. But at a high temperature of higher than70 C., it is necessary to use expensive reaction apparatus, and sincesufficient effect may be obtained at a temperature lower than 70 C., itis preferred to use a temperature below that level. In the alkylationreaction of the first step, the yield of detergent alkylate may beincreased in response to decrease in the reaction temperature employeddue to the decrease in the formation of the light alkylate. But, inreality, the formation of heavy alkylate is rather high in thealkylation reaction at lower temperatures.

On the other hand, in the second step, heavy alkylate in the alkylationproduct decreases in response to the heat treatment time, but, on thecontrary, the formation of light alkylate would be increased.

Therefore, the reaction time employed in the second step may be from 30seconds to minutes. When the alkylation reaction is carried out at alower temperature of from 5 to 10 0, heavy alkylate is formed inrelatively large amounts in the alkylation product, therefore, it ispreferred to conduct the heat treatment step in a longer period. On theother hand, when the alkylation reaction is carried out at a highertemperature of about 30 C., heavy alkylate is formed only in smallamounts, thus, the second step may be conducted for a short period oftime, since the amount of heavy alkylate is small enough to start withand longer heating only leads to undesirable formation of lightalkylate.

The second step may be conducted in the same reactor used as thealkylation reactor, or a different reactor maintained at the heattreatment condition.

If necessary, during the second step, hydrogen fluoride may be added tocompensate the loss, or other necessary procedures to preventdisproportionation reaction of the alkylate, may be employed.

It has never been expected heretofore that there can be obtained such asatisfactory result by the heat treatment of the second step of theprocess of this invention. Because there has been a sufficient reason tobelieve that the yield of the product could be decreased by such heattreatment, considering the fact that the yield of the product isdecreased as the temperature is increased in the alkylation reaction,and, in addition, there has been a fear that the exposition of thealkylation reaction mixture to a high temperature may adversely affectthe color of the product due to the thermal decomposition thereof.

Contrary to the expectations, however, in accordance with the heattreatment in the process of this invention, there occurs nocontamination of the product by the side-reactions of heavy and lightalkylates existing in the reaction system, but, there occurs a reactionconverting the heavy alkylates into the product alkylate, however alittle, which contributes to maintain the yield of product at a highlevel.

In the second step of this process, a part of byproduct dialkyl benzeneformed in the first step alkylation reaction would be converted intomono-alkylate by the trans-alkylation reaction involved. Further, whenthe first step reaction is carried out at excessively lowertemperatures, the product alkylate sometimes contains a small amount ofunreacted olefin, but such unreacted olefin may be converted intodesired alkylate in the second step of this process.

The reaction conditions employed in the alkylation reaction of the firststep mentioned above are substantially the same as those employed in theconventional alkylation reaction known heretofore.

Aromatic hydrocarbon and olefin may be used in this process in a molarratio of 3:1-2011 or more. The hydrogen fluoride catalyst may beemployed in an amount of from to 30 moles or more per mole of elefinused.

The starting olefins which may be used in the process of this inventioninclude branched chain monoolefins such as propylene tetramer andstraight chain monoolefins having 8-18 carbon atoms such as internalolefin produced either by the chlorination of straight chain paraffinfollowed by the dehydrochlorination, or by the dehydrogenation ofstraight paraffin, and a-olefin produced either by the cracking ofparaffin wax or the polymerization of ethylene.

The starting mono-olefins which may be used in the process of thisinvention further include mixtures of mono-olefin and paraffin, andmixtures of straight chain mono-olefin and branched mono-olefin.

In the foregoing explanations, mainly benzene is exemplified as the arylcompound, but other aryl compounds such as toluene, xylene, naphthalenee-tc., may be used.

The process of this invention may be carried out batchwise,continuously, or in other adequate manners.

The following examples will illustrate this invention more fully.However, it should not be construed that these examples restrict thisinvention as they are given merely by way of illustration.

EXAMPLE 1 (COMPARATIVE EXAMPLE) This example shows the relationshipbetween a reaction temperature and a Z-phenyl alkane content in thealkylates, and also the relationship between the temperature and colorof sulfonate obtained therefrom.

In the example, straight chain olefin having 10-14 carbon atoms producedby cracking of paraffin wax, was used as starting material.

Into a reactor were charged 1 moles of benzene and moles of liquidanhydrous hydrogen fluoride per mole of olefin. Into the reactor wasadded olefin dropwise at various temperatures specified in the followingtable, over a period of 5 minutes, and the reaction was continued for anadditional minutes to complete the alkylation reaction. From thereaction mixture was removed the catalyst according to the conventionalmanner, and the product obtained was distilled to separate into initialdistillate, main alkylate fraction and final distillate. The mainalkylate fraction was analyzed by gas chromatography to determinecontent of Z-phenyl alkane. Further, bromine number which correlates tocolor of the sulfonate to be obtained therefrom Was measured accordingto ASTM/D 1159.

Then the alkylate was sulfonated batchwise by reacting 1.0 mole of thesame with 1.05 mole of liquid anhydrous sulfuric acid, while dilutingwith nitrogen, at 50 C. for 45 minutes. The sulfonic acid obtained wasneutralized with sodium hydroxide to form sodium salt of sulfonic acid.Color of the sulfonate was measured by the absorbance of sulfonatesolution in 10% alcohol-water solution, using a 10 mm thick cell at awave length of 420 III/L.

The reaction temperature used and results obtained are tabulated in thefollowing table:

Reaction temperature C O.) 0 10 50 70 Z-phenyl alkane content (percent)Bromine number Color of sulfonate 6 EXAMPLE 2 (COMPARATIVE EXAMPLE) Thisexample is to explain the relationships between an alkylationtemperature and yield of alkylate product, and between the temperatureand color of the sulfonate obtained.

The reaction was conducted by charging 10 moles of benzene and 20 molesof hydrogen fluoride into an autoclave, and adding dropwise 1 mole ofpropylene tetramer to the mixture over a period of 5 minutes, withstirring while maintaining at a predetermined temperature as set forthin the following table. The reaction was continued for an additional 25minutes at the same temperature to complete the alkylation. During thereaction, the reaction mixture was pressurized to maintain a liquidstate. After completion of the reaction, the reaction mixture wasallowed to stand to separate the catalyst used. Hydrocarbon-phaseseparated was neutralized with caustic soda, washed with water, driedover calcium chloride and rectified to separate the product into a lightalkylate fraction mainly consisting of lower boiling short chain alkylbenzenes, a middle fraction consisting of desired alkylate product and ahigh boiling fraction consisting of heavy alkylate.

Then bromine number of the product alkylate which correlates to color ofsulfonated product to be obtained therefrom was determined according toASTM/D 1159. Also the alkylate product was sulfonated and the color ofthe sulfonated product was examined. The color test of the sulfonatedproduct was conducted as follows:

Into 1 mole of alkylate was bubbled 1.05 mole of sulfuric anhydridediluted with nitrogen at 50 C. for 45 minutes to give sulfonated alkylbenzene. The resulting sulfonated alkyl benzene was neutralized withcaustic soda to give sodium salt. The color of the sulfonate salt wasevaluated as extinction coefficient of 10% alcoholic solution using a 10mm. thickness cell at a wave length of 420 Ill/.L.

Reaction Temperature C.)

Yield of detergent alkylate (percent by Weight) 84 82 81 76 Brominenumber 0.018 0.009 0.005 0.002 Color oisult'ouate 0.21 0.14 0.10 0.08

EXAMPLE 3 The alkylation reaction was conducted under the same reactionconditions as in Example 2, using propylene tetramer as alkylating agentat 10 C. for a reaction period of 30 minutes. After 30 minutes of thereaction, the reaction mixture was heated up to 40 C. in the course of 1minute with vigorous stirring. Then the mixture was maintained at thesame temperature for an additional 10 minutes with stirring. Aftercompletion of the reaction, the product obtained was separated,neutralized, washed, dried, and distilled in the same manner asdescribed in the preceding example. The bromine number of the detergentalkylate was determined and also color of sulfonated product wasexamined. The results obtained are as follows:

Yield of detergent alkylate (percent by weight) 84 Bromine number 0.004Color of sulfonate 0.09

From the above table, it can be noted that in accordance with theprocess of this invention, the yield of deter gent alkylate ismaintained as high as that in the conventional alkylation reactionconducted at 10 C., while color of the sulfonated product obtainedtherefrom is remarkably improved.

7 EXAMPLE 4 The alkylation reaction was conducted in the same manner asdescribed in Example 2, at 30 C. for a reaction period of 30 minutes.After the completion of the reaction, the catalyst was removed from thereaction mixture. The mixture free from catalyst was then washed,neutralized and dried. The resulting alkylate was then subjected to aheat treatment. Into an autoclave was charged fresh hydrogen fluoride ofthe same amount as used in the previous alkylation reaction and heatedat 60 C. with stirring. On the other hand, the product obtained in thealkylating reaction was preheated at 60 C. Into the autoclave, wascharged dropwise thus preheated product instantaneously. The mixture wasmaintained at the same temperature for 2 minutes With stirring. Afterthe completion of the reaction, catalyst was removed from the mixturewhich was then washed with water, neutralized with caustic soda, driedand distilled. The bromine number of the detergent alkylate and color ofsulfonate product were determined. The results obtained are as follows:

Yield of detergent alkylate (percent by weight) 81 Bromine number 0.002Color of sulfonate 0.07

From the table shown above, it can be noted that according to theprocess of this invention, the yield of detergent alkylate is maintainedas high as that in the conventional alkylation reaction conducted at 30C., while color of the sulfonate obtained therefrom is remarkablyimproved.

EXAMPLE 5 In this example, the reaction was conducted in the same manneras described in Example 4 except that the heat treatment time andtemperature were varied. The heat treatment of this example wasconducted at 50 C. for 30 minutes and 60 minutes. The results obtainedare as follows:

Heat treatment time min. 30 min. 60 min.

Yield (gercent by weight):

Lig t alkylate 13 16 20 Detergent alkylate. 81 79 76 Heavy alkylate 6 54 EXAMPLE 6 In this example, the reaction was conducted in the samemanner as described in Example 4, except that the heat treatmentcondition was altered. The heat treatment of this example was conductedat 50 C. for 30 seconds and 1 minute. The results obtained are asfollows:

Heat treatment time 0 see. 30 see. 60 sec.

Bromine number- O. 005 0. 003 0. 003 Color of sulionate 0. 0. 09 0. 09

EXAMPLE 7 Alkylation at 10 C. Alkylation at and Heat treatment 10 C. 40C. at 40 C Yield of detergent alkylate (percent by weight) 77 75 77Bromine number- 0. 117 0. 030 0. 030 Color of sulfonate 0. 21 0. 12 0.12

From the table shown above, it can be noted that the reaction at 10 C.using straight chain olefin gives undesirably colored product and thatthe reaction at 40 C. only affords lower yield of the detergentalkylate, while both the coloring and the yield are improved in theprocess of this invention.

EXAMPLE 8 The alkylation reaction was carried out in the same manner asdescribed in Example 1 by using the same reactants and catalyst as usedtherein except that the reaction temperature was 10 C. Olefin was addeddropwise into the reactor over a period of 5 minutes, and the reactionwas continued for additional 5 minutes at the same temperature. Thereaction mixture was then heated up to 50 C. within a 5-minute period.

The heating was continued for additional 15 minutes at the sametemperature.

The reaction mixture was then treated in the same manner as in Example1, and the 2-phenyl alkane content in a main fraction, and the brominenumber and the color of sulfonate obtained therefrom were measured andexamined. The results obtained are as follows:

Content of 2-phenyl alkane percent 19 Bromine number 0.012 Color ofsulfonate 0.07

From the results obtained, it is obvious that by the process of thisinvention, the alkylate having lower 2- phenyl alkane content andcapable of affording sulfonate having desirable color property can beobtained.

EXAMPLE 9 The reaction was conducted in the same manner as described inExample 1, by adding olefin dropwise to a mixture of benzene andhydrogen fluoride at 30 C. over a period of 5 minutes, and the reactionwas continued for additional 15 minutes with stirring. After completionof the reaction, the catalyst used was separated from the reactionmixture. Into an evacuated reactor, the same amount of fresh hydrogenfluoride used as the catalyst in the previous reaction was introducedand heated at 60 C. with stirring. The catalyst-free reaction mixturewas then heated at 60 C. and was introduced into the heated hydrogenfluoride instantaneously. The reaction was continued for 10 minutes atthe same temperature. Then the reaction mixture was treated in the samemanner as in Example 1 and the Z-phenyl alkane content, the brominenumber of the alkylate and color of sulfonate obtained therefrom weremeasured and examined. The results are as follows:

Content of 2-phenyl alkane percent 20 Bromine number 0.011 Color ofsulfonate 0.07

From the result obtained, it is understood that according to the processof the invention, alkylate having lower 2-phenyl alkane content andcapable of affording sulfonates having desirable color property can beobtained.

EXAMPLE 10 The example is to illustrate the use of an internal olefintogether with paraflin as the starting material.

In this example, straight chain olefins having 10-13 carbon atomsobtained by the chlorination of straight chain paraflins followed by thedehydrochlorination of the chlorinated parafiin was used. The startingparaffin was prepared by extracting a kerosene fraction with a molecularsieve. Olefins thus obtained chiefly consisted of internal olefins andcontained 4 moles of parafiin per mole of olefins.

The reactions were repeated in the same conventional manner as inExample 1 at 10 and at 50 C., and also as in Example 8 according to theprocess of this invention.

The content of 2-phenyl alkane in alkylates and the bromine number, andthe color of sulfonates were examined. The results obtained aretabulated in the following table:

What is claimed is:

1. In a process for the production of an alkyl aryl compound byalkylating an aryl compound with a monoolefin having 8-18 carbon atomsin the presence of hydrogen fluoride, the improvement which comprisesconducting said alkylation reaction at a temperature of from to 35 C.for a period of time of from about to about 50 minutes to complete thereaction substantially, and then subjecting the resulting alkylationreaction product directly to a heat treatment at an elevated temperatureof from 40 to 70 C. for a period of time of from about 30 seconds toabout 90 minutes to form a second alkylation reaction product containingthe alkyl aryl compound.

2. The process of claim 1 wherein the hydrogen fluoride is separatedfrom said resulting alkylation reaction product, fresh hydrogen fluorideis added and the resulting mixture of fresh hydrogen fluoride and thesubstantially hydrogen fluoride free alkylation reaction product, isthen subjected to said heat treatment.

3. The process of claim 1 wherein the aryl compound is benzene.

4. The process of claim 1 wherein the mono-olefin is propylene tetramer.

5. The process of claim 1 wherein the mono-olefin is an alphamono-olefin.

6. The process of claim 1 wherein the mono-olefin has internalunsaturation.

References Cited UNITED STATES PATENTS 9/ 1958 Shiffler.

OTHER REFERENCES DELBERT E. GANTZ, Primary Examiner CURTIS R. DAVIS,Assistant Examiner US. Cl. X.R. 260-674 UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION Patent No. 3 ,474 154 October 21 1969 ToshioYamanaka et a1.

It is certified that error appears in the above identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 5, line 41, "1 moles" should read 10 moles Signed and sealed this8th day of December 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr. E.

Attesting Officer Commissioner of Patents

